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| author | David S. Miller <davem@davemloft.net> | 2012-02-21 01:37:42 +0000 |
|---|---|---|
| committer | David S. Miller <davem@gcc.gnu.org> | 2012-02-20 17:37:42 -0800 |
| commit | 3ed27cf5e7f7507dc3fec0e6ad20aab55316cb57 (patch) | |
| tree | 38e311a21b0073a0e3017df93bfd40876aa40ba6 | |
| parent | d1d7a85e534f4c388c881652f04bfe73ff71267c (diff) | |
| download | gcc-3ed27cf5e7f7507dc3fec0e6ad20aab55316cb57.zip gcc-3ed27cf5e7f7507dc3fec0e6ad20aab55316cb57.tar.gz gcc-3ed27cf5e7f7507dc3fec0e6ad20aab55316cb57.tar.bz2 | |
Explain why we don't use RDPC for sparc PIC register setup.
* config/sparc/sparc.md (load_pcrel_sym<P:mode>): Explain why we
don't use the "rd %pc" instruction on v9 for PIC register loads.
From-SVN: r184422
| -rw-r--r-- | gcc/ChangeLog | 5 | ||||
| -rw-r--r-- | gcc/config/sparc/sparc.md | 4 |
2 files changed, 9 insertions, 0 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index e12e596..df2419a 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,8 @@ +2012-02-20 David S. Miller <davem@davemloft.net> + + * config/sparc/sparc.md (load_pcrel_sym<P:mode>): Explain why we + don't use the "rd %pc" instruction on v9 for PIC register loads. + 2012-02-20 Aldy Hernandez <aldyh@redhat.com> PR middle-end/52141 diff --git a/gcc/config/sparc/sparc.md b/gcc/config/sparc/sparc.md index f70acd3..c0c1ef8 100644 --- a/gcc/config/sparc/sparc.md +++ b/gcc/config/sparc/sparc.md @@ -1352,6 +1352,10 @@ ;; Load in operand 0 the (absolute) address of operand 1, which is a symbolic ;; value subject to a PC-relative relocation. Operand 2 is a helper function ;; that adds the PC value at the call point to register #(operand 3). +;; +;; Even on V9 we use this call sequence with a stub, instead of "rd %pc, ..." +;; because the RDPC instruction is extremely expensive and incurs a complete +;; instruction pipeline flush. (define_insn "load_pcrel_sym<P:mode>" [(set (match_operand:P 0 "register_operand" "=r") |